Collimating TIR lens with focusing filter lens

ABSTRACT

A radiant energy redirecting system comprising a radiant energy transmitting body structure; the structure comprising multiple elements, each of which acts as a radiant energy redirecting module, having on its cross-sectional perimeter an entry face to receive incidence of the energy into the interior of the perimeter, an exit face to pass the energy to the exterior of the perimeter in a direction towards the reverse side of the body from the side of the incidence, and a Totally Internally Reflecting face angled relative to the entry and exit faces to redirect towards the exit face the radiant energy incident from the entry face; the body structure generally redirecting incident radiant energy towards a predetermined target zone situated apart from and on the reverse side of the body relative to the side of the incidence; and lens structure associated with at least one of the faces for redirecting radiant energy passing between the entry and exit faces via the Totally Internally Reflecting face.

This application is a continuation-in-part of U.S. Ser. No. 07/869,003filed Apr. 16, 1992, Now U.S. Pat. No. 5,404,869.

BACKGROUND OF THE INVENTION

This invention relates generally to radiant, particularlyelectromagnetic, energy concentration, redirection, and manipulation,and improves over the subject matter of U.S. Pat. No. 4,337,759. It moreparticularly concerns apparatus and method for employing a transparentlens means with elements thereof using Total Internal Reflection (TIR),in conjunction with a focusing second lens and a wavelength selectionfilter, for use such as in laser spectrometry.

Radiant energy is redirected to or from a predetermined zone or zones;such redirection having a predetermined degree of concentration and/orchromatic dispersion. The zones have sources of light, as inphotoillumination, or radiant energy receiving means for conversion ofthe redirected energy to thermal, electric, chemical, or mechanicalforms.

The prior art of radiant energy concentration and illumination ingeneral consists of two major types, as exemplified by refractive andreflective astronomical telescopes: a refractive lens positioned infront of a receiver or light source, or a retro-reflective mirrorpositioned behind a receiver or light source. The corresponding devicesin the prior art of solar energy concentration are the Fresnel lens andthe parabolic reflector, which focus solar energy on a target.Furthermore, there are non-imaging, reflecting concentrators that havethe advantage of fixed daily (non-tracking) position with only seasonaladjustments, but the disadvantage of requiring relatively largereflector areas and delivering only relatively low energyconcentrations.

Fresnel lenses are devices comprising purely refractive elements, butthey have physically inherent limitations of redirecting radiant energythat give high f/ratios and bulky concentrator structure. Moreover,linear Fresnel lenses have, for off-angles in the direction of thegrooves, focusing errors, that are also inherent in the laws ofrefraction, and that limit one-axis tracking configurations torelatively low concentration.

Parabolic reflector concentrators have seen widespread use, but aresubject to losses of received radiant energy because the receiver issituated between the source and the reflector, which is thereby shaded,preventing in particular the utilization of large heat engines at thefocus. Furthermore, the receiver is exposed to environmental degradationand thermal losses; and the inclusion of a protective transparent covermeans about the receiver will merely reduce the system's opticalefficiency.

Another reflecting system has appeared in the literature, as reported byRabl in Solar Energy, Vol. 19, No. 5. It employs a retro-reflectingmeans with elements that have two TIR faces to redirect radiant energyout the same side as it came in. Its only improvement over a metalmirror of the same shape is a potentially higher reflectivity; but thedouble internal reflection doubles the sensitivity to manufacturingerror over that of the present invention, which redirects radiant energythrough itself with only a single reflection.

SUMMARY OF THE INVENTION

It is a major object of the TIR lens to overcome the above-describedproblems of, and difficulties with, the prior art, and to provide ameans to collect and employ radiant energy in a very cost-effective andefficient manner, using a new basic tool with applications that includethe collection, concentration, redirection, and wavelength separation ofradiant energy.

The present invention, which improves over the subject matter of U.S.Pat. No. 4,337,759, is basically characterized by the use of atransparent means employing elements to redirect radiant energy by meansof TIR alone, or in conjunction with refraction, such means positionedbetween the radiant energy source and a receiver. Each element redirectsradiant energy upon a common target zone or zones, during the energy'sinternal passage through the element. A properly oriented ray entersthrough the entry face and strikes the reflective face, which redirectsit toward the exit face, the three faces comprising the active faces forthat ray. In addition, the lens means is associated with at least one ofthe faces for redirecting radiant energy passing between the entry andexit faces via the TIR face.

Accordingly, the present invention is characterized by the passage ofredirected radiant energy entirely through the transmitting body meansand out the opposite side from which it entered after transmission viaassociated lens means. This invention constitutes a third class ofradiant energy concentrators that also has applications to other formsof radiant energy redirection than concentration, such as wavelengthseparation or collimation. Other surfaces of the element may be inactivefor the ray of interest (e.g., as in solar energy concentration ofrelatively parallel rays) but may impinge upon improperly oriented rays(e.g., diffuse skylight of off-angle sunlight).

The TIR elements may be contiguous, forming a transparent cover means,or separated to allow undeflected light to pass between them, forexample to be focused by a mirror upon the back of the target, which isthereby illuminated from all directions.

Each element may redirect all of the parallel rays entering it into asingle new direction, or split them into several directions, with orwithout wavelength separation, which can be controllably achieved by theindependent, non-normal angling of the entry face and/or the exit faceto the parallel rays being redirected, or achieved by diffractiongratings upon the exit face, which can be implemented by the replicativetechniques of binary optics.

While TIR alone is limited to incident angles greater than the criticalangle and therefore to any redirective bend angles less than 180°-2critical angle (about 96° for acrylic), additional redirection ispossible with or without wavelength separation by the above-mentioned,non-normal angling of the entry and exit faces. Such large bend anglesenable a given diameter transparent means to be much closer to thetarget than a means limited to refraction alone, thereby greatlyreducing the necessary support structure. Furthermore, a transparentmeans employing up to 90° bend angles can utilize a flat mirrorextending from the target to the rim of the means, thereby doublingsolar concentration or doubling intercept efficiency for a light source.

Since a given acceptance angle (of deviation from parallelism) producesa proportional requirement for target size, the target can be bisectedby the plane of the mirror, and result in an actual target of half theoriginal size, with no decrease in acceptance angle, by insulating thehalf of the target facing away from the redirected body means.Conversely, the target can be doubled in size to give a doubledacceptance angle, and then halved by the mirror back to its originalarea. This surprising potential for halving thermal losses is unique tothe present invention, being unavailable for the parabolic reflector of90° rim angle because the plane mirror would shade the aperture, andalso unavailable for the Fresnel lens because of its far lower rimangle.

Unlike the Fresnel lens, chromatic aberration is completely independentof bend angle and can have any positive, zero, or negative valuesdesired for such wavelength-separation applications as solarillumination or bandgap-tailored photovoltaic cells. Unlike theparabolic reflector, the redirective bend angle of an element isindependent of its location, greatly adding to design flexibility.(Since the parabolic reflector is a smooth continuum, there can be noarbitrary variations in redirective bend angle from one spot to aneighboring one.)

The first of the present invention's improvements over the subjectmatter of U.S. Pat. No. 4,337,759 is the curvature of the faces of theindividual lens elements. This curvature may be provided at one, two orall three of the faces (entry, exit and TIR) and, for example, mayconstitute a concave entry face, a convex exit face, and/or a convex TIRface.

Radiant energy handling is thus improved over a flat-faceted facesystem, as for example in redirection of rays from a line or pointsource, within constraints of interior shadowing and TIR face slope, toproduce either parallel or converging output beams in a system usingmultiple faces. Also, improvements in ray collimation and focusing arerealized, and design freedom is enhanced, since each face can beindividually curved or various combination of face curvatures can beemployed to minimize aberrations, due to the finite size of the facets.

For ease of quality control of manufacturing, the curved facet faces canform spheres with centers on the axis of rotational symmetry of thelens. When an axially symmetric lens is made by molding a rigidmaterial, undercut interior faces are precluded, which limits thecurvature of those faces. This constraint is not applicable toelastomeric lens materials.

The facet design of the TIR lens has four degrees of freedom: the angleof the entry face, the angle of the TIR face, the angle of the exitface, and the position of the inwardly adjacent facet. A full designsolution requires that four requirements be used to derive these fourangles. In many of the designs illustrated below, prearranged choicesrestricted the degrees of freedom. In general, however, the requirementsare:

a) the redirection of light from source to target;

b) the full interception of light by the TIR face;

c) the full illumination of the exit face, for maximum thermodynamicefficiency; and

d) the non-interference of a facet's input and output rays by the nextfacet inwards.

Typically, a TIR lens is generated from the outermost, or rim, facetinwards in a facet-by-facet, numerically controlled iteration. The fourrequirements form a set of nonlinear equations in four unknowns to besolved for their roots. Because there is no general method of solvingsuch equations, typical computer routines apply a matrix inversionmethod that assumes quasi-linearity in the neighborhood of the solutionhyperspace. This requires some prior knowledge of this hyperspace sothat a starting point for the solution search is within the quasi-linearregime. This prior knowledge depends upon whether the facet istriangular or quadrilateral. The former give wider interfacet slotangles and thus are easier to make; but the latter add another degree offreedom, enabling a wider choice of overall lens shapes.

The angle of this fourth, optically inactive, side of the facet wouldtypically be set at the minimum draft angle for pulling the lens from amold (about 2°). In the case of small lenses with only a few facets,there is also the possibility of an adjacent facet being larger orsmaller than its neighbors, in order to raise the lens height andimprove collimation.

The relative facet positions, as determined by the non-interferencecriterion, determine the overall lens profile, which should be low orhigh depending upon the application. In a solar concentrator, the lensheight should be minimized to reduce spot size of the solar image. In aconverging or collimating TIR illumination system, it is advantageous tohave somewhat more lens height, so that the apparent size of the sourceis reduced at the central facets, and the output beam is therebytightened. This consideration does not hold for diverging TIR lenses,because only efficiency, and not beam tightness, is required.

An important use of facet curvature is in a small TIR lens with only afew facets, such as a collimator for a light-emitting diode. Moldingvery small facets may be undesirable because of difficulties in makingthe mold. Curved facet faces enable relatively large facets to performas accurately as small ones. Lenses for light-emitting diodes are ofinterest for red lamps at the rear of automobiles. In fact, the TIR lenscan be incorporated into the conventional transparent cover of an LED,greatly improving its luminous efficiency.

Further improvements over the subject matter of U.S. Pat. No. 4,337,759are:

A lens that redirects light from a source in order to focus it on a spotin front of the lens.

There are two reasons that the TIR lens is superior to conventionalellipsoidal reflectors for this application. First, the lens and itsassociated planar back mirror collect all of the output of a lightsource and focus it. The ellipsoidal reflector typically collects only afourth of a source's output.

Second, facet configurations are possible with efficient focusing power;that is, at the center of the focal spot, the entire lens would appearto be as bright as the light source itself, a condition known as "fullflashing", important for the proper functioning of microfiche and slideprojectors. Because of astigmatic aberrations inherent in theellipsoidal reflector, it is never fully flashed, producing instead amuch broader focal spot. Full flashing by the TIR lens is made possibleby faceting of the exit so that stairsteps have their "risers" parallelto inner rays then emerging from the exit face. Then, the full exit faceof the facet must be illuminated by light from the TIR face, a conditionthat can be fulfilled by curvature of the TIR face.

Furthermore, the exit face can have about the same refractive bending asthe entry face, preventing unwanted image magnification that broadensthe focal spot. The individual convex curvature on each of the facetfaces is vital to the success of this design:

entry-face curvature enables the entire TIR facet to be utilized,through a slight convergence that prevents any light from missing theTIR face;

TIR-face curvature enables the entire exit face to be illuminated, bypreventing any light from striking the stairstep risers or the adjacentTIR face; and

exit-face curvature focuses light onto the target, eliminating theeffects of finite facet size.

This focusing configuration would have two prominent applications thatconsiderably improve the light utilization efficiency of the prior art:

Imaging projectors for slides, motion pictures, or microfiche. Currentdesigns use ellipsoidal reflectors that have inherently low interceptefficiency (i.e., the fraction of the source output that actually endsup in the output image of the device).

The TIR lens of the present invention can be used in conjunction with anaspheric lens in order to remove the cosine-4th illuminationnon-uniformity typical of the prior art. This version of the TIR lenstypically has stepped exit faces, with the risers angled parallel to theconverging rays, to ensure spatial continuity of the focal cone. Thefaces of the facets can be curved so as to augment the action of theauxiliary lens.

Another advantage of the TIR lens for this application is that itazimuthally smears out any structure in the source, removing a source ofpattern noise that is inherent in the imaging action of an ellipsoidalreflector.

Illumination injector for optical fiber bundles and light pipes. Priorart here also uses ellipsoidal reflectors. The TIR lens would have afocal cone half angle matched to the acceptance angle of the target.

Light-gathering means for spectrometers that analyze the diffuselyemitted light of samples that have been stimulated to produce Raman orfluorescent light.

Conventional spectrometers typically collect this light with microscopeobjectives, which also deliver tightly focused (50 micrometers) laserlight to the sample. These objectives typically have a focal lengthequal to their diameter, so that they subtend about 50° and collect 5%of the diffusely emitted output.

The converging TIR lens can collect over half of this emission, a factorof ten improvement, greatly aiding spectral analysis because of thegreater signal to noise ratio.

A TIR lens that redirects light from a source in order to form adiverging cone of light, as in floodlighting applications. For coneangles of 45° or less, this lens is more efficient than a conventionalcongruent reflector and much more compact. This divergence can either befor uniform illumination, or it can take the appearance of effectivelycoming from a virtual source located behind the lens, with appropriatefacet-face curvatures compensating for the different distances of thefacets from the source.

Two types of linearly symmetric TIR lenses for cylindrical sources (suchas fluorescent tubes):

One that confines its output to a relatively narrow off-axis angle. Withthe prior art, this is possible only with quite deep and bulkyreflectors.

One that reduces its on-axis output and enhances the lateral output, inorder to produce uniform illuminance on a nearby surface that is beingused for indirect lighting. Such a shape appears very different fromother TIR lenses.

Linear TIR lenses have somewhat of a handicap from sagittal ray internalreflection, whereby rays emitted from the linear source at a largeout-of-plane angle with the lens cross section will encounter the exitface at a total incident angle that exceeds the critical angle for totalinternal reflection. Most of the facet designs used in radiallysymmetric lenses will, when put into linear lenses, be subject to thiswhenever the out-of-place angle exceeds 40°, which encompasses half ofall rays emitted from a Lambertian, or uniformly emitting, source. Thistrapping of light within the lens can be remedied by corrugation alongthe outer face of the lens, which unfortunately precludes manufacturingby extrusion because the cross section is no longer constant. Anothermethod is binary optics outcoupling through miniature stepped patternson the outside of the lens.

A more useful lens design would be applied to a toroidal fluorescentlamp. The TIR lens profile would have its axis of symmetry over thecircular cross-section of the toroidal lamp. The complete lens would bea figure of revolution with its axis being that of the toroid ratherthan the center of the lens profile. The more slender the toroidal lamp,the better could its light be controlled by the lens.

Presently, there are no reflectors that can collect the light of such alamp and put most of it into a forward-going beam. This toroidal TIRlens would be very useful for battery-powered fluorescent lanterns,which currently cannot provide any focusing whatsoever.

A collimating TIR lens made of silicon. Because of the high refractiveindex of this material, the refractive faces of its facets would besomewhat differently angled than those of a glass lens. The applicationfor a silicon lens is for the collimation of infrared light and theexclusion of visible light (because silicon absorbs all wavelengthsshorter than 1.1 micrometers). The purpose of this application is thejamming of the guidance sensors of heat-seeking, anti-aircraft rocketsby focused beams of pulsating infrared light. The prior art uses muchless efficient parabolic reflectors in conjunction with a siliconwindow. The silicon TIR lens would be an important new kind of infraredilluminator, as found in many night-vision systems.

The superiority of the present invention can be seen in its applicationto prisms with curved cross sections, arrays of connected linear ortoroidal prisms acting in concert, redirection of rays from a line orpoint source, concentration of spherical or plane waves, bettercollimation than parabolic mirrors, and more efficient focusing thanellipsoidal mirrors.

Another object of the invention is to provide a radiant energyredirecting system comprising:

a) a radiant energy transmitting body means,

b) that means comprising multiple elements, each of which acts as aradiant energy redirecting module, having on its cross-sectionalperimeter an entry face to receive incidence of the energy into theinterior of the perimeter, an exit face to pass the energy to theexterior of the perimeter in a direction towards the reverse side of thebody from the side of the incidence, and a Totally Internally Reflectingface angled relative to the entry and exit faces to redirect towards theexit face the radiant energy incident from the entry face,

c) the body means generally redirecting incident radiant energy towardsa predetermined target zone situated apart from and on the reverse sideof the body relative to the side of the incidence,

d) first lens means associated with at least one of the faces forredirecting radiant energy passing between the entry and exit faces viathe Totally Internally Reflecting face, the redirected radiant energybeing collimated,

e) and second lens means spaced from the exit face to receive thecollimated radiant energy and to redirect same toward the target zone.

Yet another object of the invention is to provide a system, as referredto, wherein the second lens means is a focusing Fresnel lens. Awavelength selective filter may be provided in the path of collimatedradiant energy, redirected toward the target zone; and that filter mayextend in close proximity to the second lens means and between thelatter and the first lens means. Further the first and second lens meansmay define a principal axis which passes through the target zone, andthat axis may extend normal to parallel planes defined by the secondlens means and the filter.

A further object concerns the provision of a central portion about whichthe entry, exit and Totally Internally Reflective faces extend, thecentral portion comprising a microscope objective; and a mirror may bepositioned between said first and second lens means to reflect lighttoward said central portion of said body means.

These and other objects and advantages of the invention, as well as thedetails of an illustrative embodiment, will be more fully understoodfrom the following specification and drawings, in which:

DRAWING DESCRIPTION

FIG. 1 is a vertical section in elevation showing one form of apparatusembodying the invention;

FIG. 2 is a vertical section in elevation showing another form ofapparatus embodying the invention;

FIG. 3 is an enlarged section on lines 3--3 of FIG. 2;

FIGS. 4a-4e1 are enlarged sections through elements of variousconfigurations;

FIG. 5 is a view like FIG. 1 showing a portion of a solar opticalconcentrator of somewhat different and employed configuration;

FIG. 6 is a schematic showing two devices, operating in conjunction, oneof which is like that of FIG. 1 or 5, and the other being a collimator;

FIG. 7 is an enlarged section through a collimator as used in FIG. 6;

FIGS. 8-11, 13, 14 and 15 are schematics showing different applicationsof the radiant energy concentrating means;

FIGS. 12a and 12b are fragmentary sections showing modifiedconcentrators;

FIGS. 16-18 show various curved lens surface arrangements;

FIGS. 19a-19c are sections producing light rays of varying angularity,as shown;

FIG. 20 is a section of a facet with three curved faces, illustratingthe general principles of facet design;

FIG. 21 is a section showing a further modified radiant energyconcentrating means for use with a light-emitting diode;

FIG. 22 is a section showing yet another modified radiant energyconcentrating means made of silicon to pass infrared (IR) rays;

FIG. 23 is a section showing a radiant energy transmitting body means,as in FIG. 21a, directing converging light toward a light pipe;

FIG. 24 is a section showing a radiant energy transmitting means,directing diverging light as in a floodlight;

FIG. 25 is a section showing a radiant energy transmitting means,directing light from a layer-stimulated sample to converge into aspectroscopic analyzer;

FIG. 26 is a section showing a radiant energy transmitting means,directing light from a toroidal source; and

FIG. 27 is a section like FIG. 25 but showing provision of a secondlens, and a filter, in the path of collimated light or radiation..

DETAILED DESCRIPTION

As described in U.S. Pat. No. 4,337,759, and referring to FIG. 1,radiant energy transmitting body means 10, in the shape of a cover ordome, has multiple facets or elements as at 11, each facet having anentry face to receive impingement of such radiation, an exit face topass energy to the exterior of the body, and an internal reflection faceangled relative to the entry and exit faces to reflect radiant energyincident on the reflection face toward the exit face. For example, inFIGS. 1 and 4d, a selected facet 11 has, in vertical cross section, anentry face 12 made up of stairstepped faces 12a and 12b, an exit face 13facing the zone of target 15, and an internal reflection face 14.Radiant energy, such as light, is represented by rays 16a and 16bentering the body means 10 at flat face 12a and normal thereto, andpassing internally of the facet for reflection by face 14. For thispurpose, the face may be silvered at 17. The reflected rays 16c thenpass toward and through exit face 13, normal thereto, and directlytoward the target zone.

The body means 10 may consist of solid transparent material, such asglass or plastic, for example.

The multiple facets 11 shown in FIG. 1 may extend annularly about anddefine a common axis 18; or they may extend in parallel relation (normalto the plane of FIG. 1) at opposite sides of a plane as alternativelyrepresented by 18, and which is normal to the plane of FIG. 1. In eitherevent, corresponding points on the facets define a concave surface, asfor example at 21 (defined by the tips 22 of the facets closest thetarget), and characterized in that radiant energy passing through theexit faces is directed generally toward the target zone. Tips 22 areformed at the intersections of the faces 13 and 14. Surface 21 isparabolic.

The series of facets in FIG. 1 is further characterized by the existenceof tapered gaps 23 between adjacent faces 24 and 14 of the projectingportions of the facets. Faces 24 are inactive surfaces, i.e., do notpass the radiation. See for example representative rays 25 and 26 inFIG. 1. Ray 25 is redirected by its associated facet almost 90° towardthe target, near the outer edge 27 of the TIR lens 10. Study of FIGS. 1and 4 will show that angle α (the bend angle of the ray) increases forfacets increasing in distance from axis or plane 18; and that angle β(the angularity of face 14 relative to a line or plane parallel to lineor plane 18) increases for facets increasing in distance from 18. Also,the entry faces 12 form stairstep patterns.

FIG. 1 further shows a Fresnel lens 29 associated with TIR lens or body10, and located at a mid-portion of the latter; thus Fresnel lens 29,which refracts incident radiant energy toward target 15, is located inthe path of rays 30, which are redirected the least, i.e., at thesmallest angles, toward the target. Lens 29 may be integral with lens10, for example.

Further, a reflector or mirror surface is shown at 30 spaced from andfacing the facets at the target side thereof. Surface 30 is arranged toreflect stray or divergent radiation from the extreme outward facetstoward the target. See ray 31 in this regard, and reflection point 31a.This allows target 15 to halve the area exposed to heat loss that itwould have without surface 30, since the bottom non-illuminated halfcould be well insulated.

Also shown in FIG. 1 is one form of means to controllably tilt theassembly of lenses 10 and 29 and reflector 30 to cause axis 18 to remaindirected toward a relatively moving source of radiation, as for examplethe sun. In that example, a base plate 32 supports reflector 30, as wellas the dome-shaped lens 10 and 29, via extreme outer edge portion 10a ofthe body means A ring gear 33 supports plate 32, and meshes with spurgear 34. Drive motor 35 rotates gear 34 to controllably rotate ring gear33, and control unit 36 controls motor 35. Unit 36 is responsive tophotocells 37 and 38 in such manner that the photocells remain directedtoward the light source. The photocells are suitably carried at 99 bythe plate 32, as for example near its periphery.

Target 15 may for example comprise a fluid receptacle which is heatconductive, to transmit heat to fluid in the receptacle, as for examplewater in a pipe.

In FIGS. 2 and 3, the numerals 100 and 129 designate lensescorresponding to lenses 10 and 29 described above. They are elongated inthe direction of arrow 149 and are carried by supports indicated at 150and 151. V-shaped shroud 152 has edge portions 152a connected to theopposite edges of lens body 100, so that the shroud and lenses define anenclosure.

A second and insulative tubular shroud 153 extends within thatenclosure, about a tank 154 which has fixed (nonrotatable) position. Asupport for the tank may take the form of legs indicated at 155 and 156,bearings being provided at 157 and 158 to allow tank and shroud rotationabout central axis 159, along with the lens assembly. The shroud 153 iscut-away at locations 160 and 161 to allow entry of radiant energy fromthe lens assembly, to be absorbed by the tank, while heated air isprevented from escaping gap 162 by wipers 163; the enclosure has areflecting interior surface 152b.

Cool liquid, such as water, enters the tank via pipe 164, is heatedtherein, and discharges into the tank lower end at 164a. Warmed liquidslowly flows at 200 back up the tank, being further heated by contactwith the exterior of pipe 164, the liquid leaving the tank at outlet165. A sacrificial anode 166 in the water 200 is adapted to corrode,electrolytically suppressing any corrosion of the tank itself. Also, aback-up heater 167 in water 200 is supplied with electrical current toheat water in the tank as when solar radiation is blocked ornon-existent, as at night. An air-gap may be provided at 162 betweenshroud 153 and the tank itself. Sun tracking mechanism is indicated at170, to rotate the assembly to maintain the sun's rays incident normallytoward the lenses 100 and 129, i.e., in direction 171 in FIG. 3.

In operation, all radiation directed parallel to arrow 171 and strikingthe lenses 100 and 129, is redirected toward the tank, as facilitated bygaps 160 and 161, to heat the liquid in the tank. Also note windows 162and 163. Wide angle, i.e., almost 180°, collection of the solar rays isemployed, as described above in FIG. 1. The gap walls 153a arereflective, and may have other, curved shapes besides the straight linesshown here, for the purpose of secondary concentration. Stray radiationfrom the diffuse sources, such as skylight, is absorbed by blackeningthe surface 153a of shroud 153 and of lens support fin at 130.

Various geometric configurations of elements and arrays of elements arepossible, wherein various element configurations have the same relativeangles of the three active faces, but differing deployments within thetransparent means; e.g., the TIR face can be in faceted slots on eitherside of the body means or on the walls of tunnels within the latter,while the entry faces can be on faceted steps or even on a completelysmooth cover surface.

In FIG. 4a, tunnel 40 forms TIR face 41, while exit face 42 hasstairsteps 42a and 42b. In FIG. 4b, slot 50 is on the entry side of thebody means, having TIR face 51 and entry face 54. Exit face 52 hasstairsteps 52a and 52b. In FIG. 4c, tunnel 60 forms TIR face 61, andentry face 62 and exit face 64 are on smooth continuous surfaces.However, TIR face 61 must be longer than TIR faces 41 of FIG. 4a or 51of FIG. 4b, because of the refractive bending of ray 63 by entry face62. In general, the length of a TIR face relative to facet width 65 is:

    TIR LENGTH=cos δ /(cos η cos η)

where η is the incident angle of ray 63a with surface normal 66, δ isthe angle of the refracted ray 63b with 66, κ the incident angle ofreflected ray 63c with exit surface normal 67, and λ the angle ofrefracted by 63d with 67. The relationships of these angles are given bySnell's law:

    sin η=n sin δ, and sin λ=n sin κ

where n is the index of refraction of the body means material. Forcontiguous elements to redirect to a target all the parallel raysincident upon them, neighboring elements must be relatively positionedeverywhere on or above a parabola with the target as its focus and a rimslope equal to half the rim angle (i.e., the redirective bend angle ofthe outermost elements).

In FIG. 4d, "extreme" ray 16c must clear tip 22 of the inward adjacentfacet, while the other extreme ray, 16b, must clear top 27 of slot 23.These clearance conditions require that the lens slope angle η begreater than or equal to the TIR tilt angle, which is geometricallyequivalent to tangent line 22 being on or above the parabola.

Note that all of the configurations of FIG. 4 have the same bend angleα, and except for FIG. 4c, the same normal entry and exit faces. See forexample the elements 311 of the "cover" 310 in FIG. 5, above theparabola 321 tangent to the tips 322. See also line 324. Those tipsbelow the parabola, such as for a quarter-circle 325 with the same slopeat the rim, would in this stairstep configuration suffer someinterelement impingement, about 10% for both cylinders and spheres; butthe use of a thin, flexible, inflatable dome for a transparent covermeans might be worth such a loss, especially since the untargeted rayswould still be redirected to a locus within the cover means, to assistthe pressurization by heating the enclosed air. See FIG. 11 for anon-impinging circular configuration.

An alternative facet style seeks to minimize such impingement losses byconcentrating the rays before they strike the TIR face, which canthereby be smaller to reduce said impingement. Convex and concave entryand exit faces will do this, though with some decrement of the cover'sconcentration ratio or acceptance angle, which for some applications isfar outweighed by bringing the transparent redirecting means even closerto the target.

For the smaller bend angles, difficulties are encountered in thenarrowness required of the tunnels or slots 23 in FIG. 4d forming theTIR faces of the low bend-angle elements. This can be somewhatalleviated by raising the profile of the transparent means 310 above theparabola 321 to widen the slots and tunnels beyond their minimum widths.Another form of such an alleviation is a backbending exit face, 311 ofFIG. 5, so angled that its refractive redirection opposes theredirection of the TIR face, which can thereby have a greaterredirective bend angle with a less steep slope, giving wider tunnels orslots.

In FIG. 5, note that ray 330 strikes the exit face 11 non-normally, sothat ray 330a is bent back toward the target. This enables a wider slot323 than if the exit face was normal and the TIR face was at a steeperangle. The above-mentioned convex entry face will also widen the slotsor tunnels.

Another method of widening the slots is the faceted exit face, shown inFIG. 4e. Here slot 70 has been opened until it nearly impinges uponextreme ray 73b. Exit face 74 has miniature stairsteps 74a and 74b,respectively normal to and parallel to reflected ray 73b. Alternatively,a thin, microstructured series of elements of high refractive index (sayn=4) can be embedded in the body means to form more favorably shapedelements. The particular manufacturing method and design applicationwill determine the place of transition to a Fresnel lens, oralternatively to a window, that passes rays to a small parabolicreflector below the target, which is thereby illuminated from a fullcircle of directions.

Another possible configuration would have the outer parts of theredirecting means sending radiant energy to a central target while theinner parts redirected energy to outer targets using only large bendangles throughout. All these configurations are derivatives of the basicmethod of this invention: upon multiple TIR-transmitting elements,properly placed entry, exit, and TIR faces redirect radiant energy to apredetermined target zone, or into a predetermined target solid angle.

Also usable is a cover means (as at 10 or 110) whose focal length can beshorter than any parabolic mirror with concentrations twice as high, butwhich is free from shading and presents a convex surface with loweraerodynamic drag than the concave parabolic mirror. Its target is nearthe center of gravity and closer to the ground than that of theparabolic reflector making fixed receiver means easier to design andmaintain. Finally, the nearly 100% reflective efficiency of the TIRfaces give much greater potential for high efficiencies than does theparabolic mirror.

In FIGS. 1 and 5, it will be understood that the elements 11 and 311join together, integrally and continuously, to form a radiant energytransmitting means in the general form of a cover. The latter has anenergy entry surface (top surface in FIG. 1, for example) and an exitsurface (bottom surface in FIG. 1) lying on opposite sides of the cover.The cover causes radiant energy leaving the exit surface to have agenerally different direction than the direction of energy incidence onthe entry surface. Also, multiple TIR faces are situated on the exitsurface adjacent slots proximate the exit surface, as referred to above.The entry surface has a faceted stairstep configuration. The exitsurface of the cover lies beyond and further from the target than aparabola (see 21 and 321). The cover may be constructed of transparentmaterial, as for example plastic.

FIG. 8 schematically shows a means 410 corresponding to the means 10 ofFIG. 1 or 310 of FIG. 5, or equivalent. A target zone is shown at 415. Aretro-reflector means 412 is spaced behind and facing the target zone soas to redirect radiant energy upon the target zone. See ray 413.

FIG. 9 schematically shows a radiant energy source means (as for examplea light source) at 430 at the target zone. Radiant energy emitted by thesource means 430 is redirected by the body means 435 (like 10 or 310) inreverse relation. See ray 436.

FIGS. 10a and 10b show two variations of a "uni-bend" lens with uniformfacets extending annularly about a cylindrical target. In FIG. 10a, allthe facets 444 of conical body means 440 bend rays 443 through 90° ontocylindrical target 441. In FIG. 10b, flat body means 445 has identicalfacets 448 bending rays 447 through 45° upon cylindrical target 446.

FIG. 11 shows a structural means 460 enclosing the space 461 behind theexit face of the cover means 459 (like 10 or 310), so thatpressurization of the atmosphere of space 461 will hold the flexiblecover means in its distended or circular shape, with center of curvatureat point 426. See target zone 462, pressurization means such as a pump463 and ray 464. A thin film 465 adheres to the inside of cover means459, having miniature sawtooth facets 467 as shown in the insert.

FIG. 12a shows a plurality (two for example) of target zones 470 and 471to receive radiant energy from the transmitting body means 472 (like 10or 310). Each element 473 redirects energy in a plurality of directions,toward the target zones. Thus, each element 473 may be like element 10or 310 described above but have a TIR face divided into two sub-faces474 and 475 at slightly different angles to accomplish the reflection ofthe two rays 476 and 477, respectively directed by the faces 474 and 475toward the two target zones.

In FIG. 12b, TIR face 453 is the exit face for ray 451; while TIR face454 is the exit face for ray 452. This symmetrical case of twin 60°bends may be varied to give two different right and left hand bends,with differing division of the incoming radiant energy.

In FIG. 13, the cover means 480 (like 10 or 310) has different groups ofelements redirecting radiant energy toward different target zones. Thus,the elements at locus 481 direct radiant energy toward target 482; andthe elements at locus 483 direct energy toward target 484. See rays 485and 486.

In FIG. 6, cover or body means 510 corresponds to 10 or 310 describedabove. A secondary radiant energy redirecting means is provided at 520to intercept the radiant energy from body 510 and to redirect it. Seerays 521 with segments 521a falling on body 510; redirected segments521b falling on body 520; and secondarily redirected segments 521ctransmitted by body 520.

FIG. 7 shows body 520 in detail, with entry faces 530, exit faces 531,and TIR faces 532. The rays 521c are parallel, in this instance, i.e.,collimated, so that means 520 may be regarded as a collimator.

The means 550 shown in FIG. 14 is like 10 and 300, except that the exitfaces 551 are individually angled relative to radiant energy passingthrough them, so as to cause reflective redirection of the radiantenergy. See beam 552 refracted at face 551. Also in FIG. 14, the exitfaces 551 may be considered to refractively redirect radiant energy inpartial opposition to the redirection by the TIR faces 553, the latterextending at less steep angles (than in FIGS. 1 and 5) so as to widenthe slots 554. Note also in FIG. 14 that the entry face is smooth andunfaceted, at 556, and that exit face 551 is parallel to refracted ray552b, giving the maximum backbend and the lowest possible slope of entrysurface 556, which in fact is lower than the parabola 321 or thequarter-circle 325 in FIG. 5.

In FIG. 15, the body means 560 is like that at 10 or 310, except that itutilizes the variation index of refraction that varies with thewavelength of the radiant energy, so as to constitute a wavelengthseparating, radiating energy redirecting, transmitting body means. Twotarget zones 561 and 562 are shown, and are spaced apart to receivedifferent wavelengths of the wavelength separated, redirected, radiantenergy. See incident ray 563 which separates into ray 563a of onewavelength directed toward target 561, and ray 563b of anotherwavelength directed toward target 562.

Also in FIG. 15, either target may be considered as a means to convertradiant energy to electricity. One such means is a photovoltaic cell.Such a device may be located at the target zones in FIGS. 1 and 5. InFIG. 15, one target may comprise a photoillumination means receivingvisible wavelengths; and the other target may comprise a thermalreceiver receiving invisible wavelengths at zone 561.

When a source of radiant energy is placed in zone 562, the visiblewavelength rays will follow the reverse path of rays 563, i.e., becollimated, while the invisible longer wavelength heat rays will bediverged more outward from the visible beam, so that spotlights onactors will not subject them to a heat load several times greater thanthat of the visible radiation.

Certain aspects of FIGS. 1-15 were also discussed in prior U.S. Pat. No.4,337,759.

FIG. 16 may be considered to correspond generally to FIG. 4a or FIG. 4b,i.e., to present a lens body 600 having an entry face 601, a TIR face602, and an exit face 603 on the body 600. Such faces 601 and 603 may befaceted, as in the styles shown in FIGS. 1, 3, 7, 8, 9, 10, and 13.Rather than all such faces being flat, face 601 is convexly curved, awayfrom the body 600, as shown; whereas faces 602 and 603 are flat, aspreviously described. Diverging entry rays 605 are refracted at 605a forreflection at 605b, and travel at 605c toward face 603. The rays passthrough exit face 603 and are in general refracted to travel externallyat 605d, as shown. If exit face 603 was convexly curved, then rays 605dcould be converging. The curvature of entry face 601 eliminates thedivergence and keeps any rays from missing TIR face 602.

In FIG. 17, entry face 611 is flat, as is exit face 613; however, TIRface 612 is concave toward the incident ray side of that face, as shown.Diverging entry rays 615 pass through face 611 and travel at 615a,within body 610, for reflection at 615b, at different points and angles,for travel at 615c toward face 613. The rays pass through that face, andare in general refracted, and travel externally at 615d, as shown. Thecurvature of the TIR face 612 has made rays 615d parallel, whilerestricting the amount of exit face that is used, enabling the entirelens to have a higher profile.

In FIG. 18, entry face 621 is flat, as is TIR face 622; however, exitface 623 is concave away from the body 620, i.e., away from TIR face622, as shown. Entry rays 625, which may be parallel, pass through faceand travel at 625a, within body 620, for reflection at 625b at differentpoints and angles, for travel at 625c toward face 623. The rays thenpass through that face and are in general refracted to travel externallyat 625d, as shown. Exit face 623 is fully flashed, as would be desirablefor a converging TIR lens.

Other possibilities are as follows:

    ______________________________________                                                  flat           convex  concave                                      ______________________________________                                        entry face                   x                                                exit face                          x                                          TIR face           x                                                          B                                                                             entry face  x                                                                 exit face                          x                                          TIR face           x                                                          C                                                                             entry face                   x                                                exit face   x                                                                 TIR face           x                                                          ______________________________________                                    

In FIGS. 19a, 19b and 19c, the bodies 650, 660 and 670 are closelysimilar to body 740 shown and described in FIG. 21. The angularities ofthe annular facets are slightly varied, so that the body 660 producescollimated light rays 664; body 650 produces converging light rays at654; and a body 670 produces diverging light rays 674. The light sourcein each case is shown at 680. In each case, the top surface 659, 669,and 679 of the lens is circularly curved in the section shown, orspherically curved for an annular lens.

In FIG. 20, lens body 700 acts as a converging TIR lens, in the samemanner as lens 650 in FIG. 19a. Its performance is superior because ofits full flashing, which gives more effective focusing, and higherprofile, and which leads to smaller angular magnification of the lightsource, and a smaller focal spot. Upper light ray 701 and lower lightray 702 are the defining rays for the calculation of the angles of theboundaries of facet 703 and of the position of inwardly adjacent facet704. The slope of lens profile line 705 is to be maximized. The definingrays are generally diverging but can come from different parts of thelight source; for example, upper ray 701 comes from the bottom of thelight source, while lower ray 702 comes from the top of the lightsource, so that they constitute the extreme rays of all light emitted bythe source.

If the facet-defining upper and lower rays are not the extreme rays ofthe light source, then some fraction of its output light will beredirected by the lens into the output rays. Such a case may occur ifthere is a tradeoff between this fraction and the tightness of thefocusing, to be resolved by the particular application of the lens.

Facet 703 is defined by notch 703n (shown here as a fillet), tip 703t,upper point 703u of entry face 706, and on exit face 707, outer point706o and inner point 706i. Inwardly adjacent facet 704 provides threelimiting points that act analogously to pupils of conventional opticalsystems: tip 704t defines upper ray 701, while both notch 704n and outerexit face 704o must be cleared by lower ray 702. The convex curvature ofentry face 706 accommodates the divergence of the defining rays byassuring that upper ray 701 does not miss TIR face 708 and that lowerray 702 does miss notch 704n.

For the sake of diagrammatic clarity, exit face 707 is relatively closeto TIR face 708. A thicker lens with a more distant exit face wouldemploy convex curvature (as on the TIR face 708c) to assure that thedefining rays do not miss the edges of exit face 707. If they did miss,they would not be lost, since they would totally internally reflect onriser faces 709 or 710, and enter the lens output with only modestangular errors. Riser face 709 is angled to just clear lower ray 702,after it has left the lens. Optically inactive face 711 is kept at aminimum draft angle determined by the manufacturing method (forinjection molds, it is typically 2° off the mold-pulling direction).Face 711 assists maximizing of lens profile by enabling entry face 706to be angled more downward than is the case with lens 650 of FIG. 19a,where there is a straight line between a facet tip and the notch of theinwardly adjacent facet.

In summary, a unique determination of the four angularities of the facet(three for its faces and one for the lens profile) requires fourconditions: (1) overall bend angle; (2) upper ray falling on the TIRface; (3) lower ray clearing notch of the inwardly adjacent face; and(4) lower ray clearing the outer edge of exit facet of the inwardlyadjacent facet. The curvatures of the three optically active faces ofthe facet are individually determined:

(1) entry-face curvature helps to maximize the slope of the lens profileline, by allowing the tip of the inwardly adjacent facet to rise whilekeeping the higher upper ray from missing the TIR face (this reduces thedivergence of the output light of the inner facets of the lens byincreasing their height above the source);

(2) TIR-face curvature also helps to maximize lens slope by allow thenotch of the inwardly adjacent facet to rise; in addition, TIR-facecurvature enables the exit face to be fully flashed, an importantcharacteristic for several illumination applications;

(3) exit-face curvature minimizes the size of the focal spot ofconverging TIR lenses, and minimizes the beam divergence of collimatingTIR lenses.

Non-circular profiles of these curved faces may be selected in order toprovide uniform illumination by the facet.

In addition, all the facets of the lens could be designed to have thesame size focal spot, which would then be uniformly illuminated. Thisdiscussion of FIG. 20 may be considered an important aspect of theinvention, improving over or not suggested by, subject matter of U.S.Pat. No. 4,337,759.

In FIG. 21, the axis of the annular, radiant energy transmitting body740 appears at 751. The body has multiple annular facets 742 to 746which are generally concentrically arranged but having tips 742d to 746dprogressively closer to plane 750 normal to axis 751. Face 742a of facet742 is convex toward face and face 742b is concave toward face 742a inthe section shown. This relationship obtains for other facets, as shown.

A light-emitting diode (LED) 758 is located at the intersection of plane750 with axis 751 and emits light rays toward the body 740. Ray 753passes through face 742a, is refracted toward TIR face 742b and isreflected toward and passes through upper flat face 748. See also ray752 passing through face 743a, reflecting at TIR face 743b, and passingthrough upper face 748a, angled as shown. All rays passing upwardlybeyond faces 748 and 748a are collimated. The transverse width of thebody 740 may be from 0.12 to one inch, for example, and the transparentbody 740 may consist of molded plastic material. A refractive sectionwithout facets appears at 719. Smaller ratios of lens diameter to LEDsize may have outermost facets large, and successively inward facetssmaller, in order to have a higher lens profile and better collimationcurved facets are necessary for.

In FIG. 22, the radiant energy transmitting body 760 may have the samegeneral construction as shown in FIGS. 20 and 21. The lens body 760consists of silicon, or a similar material, for passing infrared rays,but blocking visible light rays, while transmitting infrared rays. Anarc lamp radiant energy source is shown at 764, at the same position asthe LED in FIG. 20.

A reflector surface 765 may be employed to extend in plane 766corresponding to plane 750 in FIG. 21 with a parabolic section 762. Theinfrared rays emanating at 767 are typically collimated but may bedivergent or convergent, as in FIGS. 19a and 19c. Note that unfacetedcentral section 770 refracts rays, as shown. The arc light source at 764may be produced by anode and cathode elements 764a and 764b. Top exitsurface 759 is circularly curved in the section shown; but the lens mayhave external, stairstep faceting. Protective transparent envelope 769keeps outside air away from the arc.

In FIG. 23, the body means 780 may have the same or similar constructionas that of FIG. 19a, for producing and directing convergent light at 781into the entrance end 782 of a light pipe 783. The lens has an upwardlyconvex arcuate upper exit surface or face 785, an entrance face or faces786, and a TIR face or faces 787. Faces 786 and 787 taper downwardlytoward plane 790, corresponding to plane 710 in FIG. 21. A central lightsource 788 is positioned in the manner of the LED in FIG. 21. A planarback mirror 789 extends in plane 790 corresponding to plane 710 andfaces upwardly. This device may input up to 80% of the light into pipe783, rather than 10% of the light as via a conventional ellipsoidalreflector.

In FIG. 24, the body means 800 may have the same or similar constructionas that of FIG. 21c. Circularly curved top surface 801 is curveddownwardly. The lens axis, in the case of an annular set of facets, isindicated at 802. Facets are seen from 803 to 812. A typical annularfacet 809 has an entrance face 809a and a TIR face 809b. Note ray 820path passing through face 809a and face 801, and totally reflected atface 809b. In the section shown, each of the faces 809a and 809b isflat. All entry faces have draft in the direction 822, for ease ofmolding. The lens is transparent and may consist of molded plasticmaterial.

A light source 825 is located on axis 802, and just above the plane 826,is within the confines of the hollow lens, as in the above examples; andthe rays 827 emanating from face 802 diverge, as in a floodlightapplication. The circular section half-angle subtended by the surface801 is typically less than 45° and greater than 25°, and is typicallyabout 35°.

In FIG. 25, lens body 850 is the same as that of FIG. 21a, except thatthe central refractive means has been replaced by microscope objective854, which can slide axially inside the lens to focus on sample 851.Characteristic diffuse (i.e., in all directions) emission 856 fromsample 851 is collected by lens 850 and focused on analyzer entranceslit 852. Collimated laser beam 855 is reflected by mirror 853 intoobjective 854 and focused on sample 851. Mirror 853 is removable inorder to use microscope objective 854 to view sample 851 and exactlyadjust its position. Lens body 850 could extend downward below sample851 to collect even more of the diffuse emission. Sample 851 may be aglass capillary containing a gas or liquid, a gold hemisphere coatedwith a sample substance, an integrated circuit on a production line(checking material composition or contamination), or a biological tissuesample.

In FIG. 26, lens body 860 has a cross-section with axis 863, in order toaccommodate toroidal (typically fluorescent) light source 861. Beneaththis lamp is annular involute reflector 862, with disc-shaped, planarmirror section 864 inside it and annulus mirror 865 outside it. Annularlens 866 refracts ray 868, which was reflected from involute 862. Ray869 is exactly analogous to ray 820 in FIG. 24. Ray 867 is redirected byfacet 870. The overall device of lamp, lens, and reflector comprise acompact floodlamp that offers much narrower divergence and much higherefficiency than possible with the prior art of reflector design.

Referring now to FIG. 27, the lens body 950 is the same as shown in FIG.19b or as in FIG. 25, modified to collimate light or a laser beam,supplied as indicated at 955. A light source or light-emitting target(laser for example) 951 transmits light to faceted side of the TIR lensbody 950, the latter redirecting the light rays, as shown by the brokenlines 956 and 980, to pass through first refracting lens means atsurface 950a and emerge as collimated light at 955. Such light thenimpinges on and passes through the wavelength selective filter 982 andthen through a second lens means 983 indicated in the example as afocusing Fresnel lens. The latter redirects or focuses light at 984 ontothe sample, or an analyser, 952.

A wavelength-selective filter 982 is used to remove passively scatteredlight of the collimated laser beam 955, while allowing passage offluorescence wavelengths, such as those generated in Raman spectroscopy,for stimulated emissions at 952. The filter 982 extends in a planenormal to principal axis 986 defined by the lens 950 and by lens 983,the filter requiring normal incidence of light for good wavelengthselection, since the filter wavelength depends upon the angle ofincidence. The filter typically removes the laser wavelengths. Theauxiliary or second lens means 983 can also act to reduce anyaberrations introduced by the annular TIR lens 950.

Also shown, as in FIG. 27, is a microscope objective lens 954 which canslide axially in a bore in lens 950, and focus auxiliary source light965 onto the target or laser 951. Note the cylindrical periphery 970 of954 parallel to axis 986, and sliding in bore 967 of lens 950. A meansto adjustably move objective lens 954 axially is schematically shown at968. Auxiliary source light 965 may be redirected by mirror 953, asshown, toward lens 954, for focusing onto the target 951.

We claim:
 1. A radiant energy redirecting system comprisinga) a radiantenergy transmitting body means, b) said means comprising multipleelements, each of which acts as a radiant energy redirecting module,having on its cross-sectional perimeter an entry face to receiveincidence of said energy into the interior of said perimeter, an exitface to pass said energy to the exterior of said perimeter in adirection towards the reverse side of the body from the side of saidincidence, and a Totally Internally Reflecting face angled relative tosaid entry and exit faces to redirect towards said exit face the radiantenergy incident from said entry face, c) said body means generallyredirecting incident radiant energy towards a predetermined target zonesituated apart from and on the reverse side of said body relative to theside of said incidence, d) first lens means associated with at least oneof said faces for redirecting radiant energy passing between said entryand exit faces via said Totally Internally Reflecting face, saidredirected radiant energy being collimated, e) and second lens meansspaced from said exit face to receive said collimated radiant energy andto redirect same toward said target zone.
 2. The system of claim 1wherein said first lens means is defined at least in part by saidTotally Internally Reflecting face.
 3. The system of claim 1 whereinsaid second lens means is a focusing Fresnel lens.
 4. The system ofclaim 3 including a wavelength selection filter in the path of saidradiant energy collimated and redirected toward said target zone.
 5. Thesystem of claim 1 including a radiant energy transmitting source fromwhich radiant energy is transmitted for incidence on said entry face. 6.The system of claim 1 including a radiant energy transmitting sourcefrom which radiant energy is transmitted for incidence on said entryface, and wherein said entry face is oriented to receive collimatedlight rays from said source.
 7. The system of claim 1 wherein theTotally Internally Reflecting face is a body boundary, so that the indexof refraction "n" of the substance of said transparent body means atsaid boundary gives total internal reflection of all radiant energywhose incident angle with the normal of said boundary at the point ofincidence exceeds Brewster's angle, which equals the inverse sine of thereciprocal of "n".
 8. The system of claim 1 wherein said perimeters ofsaid elements project from said cross section to extend linearly, inparallel relation, said entry faces facing said incident radiant energy,said exit faces facing said target zone.
 9. The system of claim 1wherein said perimeters of said elements project from said cross sectionto extend annularly about, and define a common axis, said entry facesfacing said incident radiant energy, said exit faces facing said targetzone.
 10. The system of claim 1 including a Fresnel lens associated withsaid body means and located in a mid-portion of said body means so as toredirect radiant energy through relatively small angles toward thetarget zone.
 11. The system of claim 1 including a retro-reflectingmeans spaced behind and facing said target zone so as to redirectradiant energy upon said target zone.
 12. The system of claim 1including a radiant energy source means situated in said target zone,and radiant energy emitted by said source means being redirected by saidbody means in reverse relation to the transmission by the body means inclaim
 1. 13. The system of claim 1 including a radiant energyredirecting means situated at said target zone.
 14. The system of claim1 including a wavelength selective filter in the path of said radiantenergy redirected toward said target zone.
 15. The system of claim 14wherein said filter extends in close proximity to said second lens. 16.The system of claim 15 wherein said filter is located between said firstlens means and said second lens means.
 17. The system of claim 14wherein said filter and said second lens means define parallel planes.18. The system of claim 1 wherein said first and second lens meansdefine a principal axis which also passes through said target zone. 19.The system of claim 17 wherein said perimeters of said elements projectfrom said cross section to extend annularly about, and define a commonaxis, said entry faces facing said incident radiant energy, said exitfaces facing said target zone, and said axis is normal to said parallelplanes.
 20. The system of claim 1 wherein said body means has a centralportion about which said entry, exit and Totally Internally Reflectivefaces extend, said central portion comprising a microscope objective.21. The system of claim 20 wherein said body means has a central portionabout which said entry, exit and Totally Internally Reflective facesextend, said central portion comprising a microscope objective.
 22. Thesystem of claim 21 including a mirror positioned between said first andsecond lens means to reflect light toward said central portion of saidbody means.
 23. The system of claim 21 including a positioned betweensaid first and second lens means to reflect light toward said centralportion of said body means.